Sewage pumping or lift stations are typically part of a wastewater treatment system of a municipality. The pumping station is provided where the terrain requires that the wastewater be piped from lower to higher elevations. Sewage pumping stations typically include two basic components; namely a sewage receiving or collecting chamber, commonly referred to as a "wet well", and a chamber or housing containing the pumps and associated control equipment for lifting the sewage collected in the wet well to a higher elevation, commonly referred to as a "machinery chamber".
Over the years many different types and designs of sewage pumping stations have been developed in the sewage pumping art to lift or transfer sewage wastewater and other types of industrial wastewaters. The art has designated the different types of sewage pumping stations into the "wet pit" type and the "dry pit" type. The wet pit type includes pumping stations in which the pumps are positioned within the wet well below the liquid sewage level. The dry pit type includes those stations in which the pumps are positioned outside of the wet well and not submerged in the liquid sewage. The present invention is directed to an improved dry pit type of pumping station.
There are many different types of dry pit type pumping stations. For example, there are buried pumping stations, above-grade pumping stations, wet well mounted pumping stations and recessed wet well mounted pumping stations. The buried pumping stations and the above-grade pumping stations typically include a sewage receiving wet well positioned adjacent to a machinery chamber. The wet well mounted pump stations and the recessed wet well mounted pump stations typically include a machinery chamber mounted above a sewage receiving wet well. The present invention is directed to the buried and above-grade types of pumping stations and most particularly to the buried type of pumping station having a factory built steel machinery chamber.
Buried type pumping stations generally include a buried sewage receiving wet well, typically of cylindrical concrete construction, and a buried machinery chamber which contains the pumps and associated control equipment. The machinery chamber may be of field erected concrete construction or of factory built steel construction, the latter being more economical to manufacture and install and therefore generally preferred. The machinery chamber is typically defined by a substantially flat floor and an upstanding sidewall extending upwardly therefrom. The floor of the machinery chamber is typically reinforced by a plurality of base beams secured to the undersurface thereof. At least one sewage pump means is positioned above the floor within the machinery chamber. The sewage pump means includes a base member above which is mounted the pump volute and the pump motor. A suction pipe extends vertically downwardly from the volute through the base member and extends horizontally across the floor and out the sidewall of the machinery chamber into a lower portion of the wet well. A discharge pipe extends horizontally outwardly from the volute and through the sidewall of the machinery chamber. The sewage from the wet well is pumped from the wet well through the suction pipe into the volute and then through the discharge pipe out of the pumping station.
In order to control the operation of the sewage pump means dependent upon the liquid level in the wet well, an air bubbler system is typically utilized. Such systems typically include air lines, air compressors and air rate controls. The air lines extend from the machinery chamber into the wet well, passing through the respective sidewalls thereof. It is also well known in the art to utilize displacement swithces suspended by wires in the wet well, which wires extend from the wet well into the machinery chamber. Further, it has heretofore been proposed to utilize pressure switch arrangements which communicate with a section of the suction line within the machinery. An example of such an arrangement is disclosed in U.S. Pat. No. 3,842,224, assigned to the same assignee as the present invention. A sump pump is typically provided in a sump well, formed in the floor of the machinery chamber, containing a sump pump to lift liquid collected therein through a discharge line extending from the machinery chamber into the wet well.
The pumping stations of the designs described hereinabove have served the industry quite well over the years. However, there have been various problems associated with the operation, construction and maintenance of these pumping stations, to which the present invention is intended to overcome.
There have been problems associated with the connection between the sewage receiving wet well and the sewage pump means. As indicated above, this connection is typically accomplished by utilizing a suction pipe made from standard piping, usually of larger size than the designated pump size if the flow rate is high. This presents the problem of how to seal the suction pipe to the sidewalls of the machinery chamber to prevent infiltration of ground water into the machinery chamber in buried stations and the natural elements in above ground stations. In a preferred construction where the wet well and the machinery chamber are supported on a common slab or support, it has heretofore been necessary to provide a special bottom construction in the wet well to raise the bottom thereof to approximately the height of suction pipe or to somehow convey the suction pipe down to the level of the floor of the wet well. The present invention solves these problems without special construction.
There have also been problems associated with the fact that the suction pipes lay across the floor in the machinery chamber and require the use of ell pipe sections and special fittings and other pipe sections, all of which take up valuable floor space in the machinery chamber. The suction piping inside the machinery chamber must be blasted or otherwise cleaned and painted to resist corrosion. Further, the suction piping must be installed in such a manner as to prevent piping strains on the pumps which are mounted on separate rigid bases, which bases must be leveled to prevent piping strains. The bases are fabricated parts that require cleaning, painting, careful layout and masking of the mounting bolts. This is also a source of resonant frequency vibration problems. The present invention solves these suction pipe problems and utilizes standard pipe fittings.
There have further been problems associated with the requirement that the control panel be positioned over the tops of the operators of the discharge valves associated with the discharge pipe. The necessity of the bases beneath the pumps for the piping requirements as discussed above, places these discharge valves in a relatively high position in the machinery chamber, requiring an even higher control panel mounting, thereby resulting in a greater machinery station height and sometimes less accessible switches. The present invention solves these problems by eliminating the necessity of mounting the pump on support bases.
There have been problems associated with the necessity of having external connections between the sump pump discharge line and controls associated with the sewage pumps and the wet well. These connections typically have to be made by the contractor. The present invention eliminates these external connections, and in so doing, faciliates the operation of the station by positioning all the equipment in close proximity to the control panel.
Further it has heretofore been difficult to test the operation of the entire pumping station and piping without the machinery chamber shell in place. It was necessary to remove and add piping during such testing, and after completion of the testing, the piping must be reinstalled to the shell. Further, it was not possible to test the pump control switches and sump pump as it will operate in the field. The present invention solves these problems by permitting the testing of the entire pumping station without the machinery chamber shell in place and without the necessity of removing and adding piping.